Conventionally, a liquid crystal display device includes a plurality of scanning signal lines (gate signal lines) and a plurality of video signal lines (source signal lines) which intersect with each other, and includes a liquid crystal panel having display pixel sections, disposed in a matrix manner, each of which is provided in each of areas sectioned by both the signal lines so as to be connected to each gate signal line and each source signal line. Each display pixel section includes: a liquid crystal capacitor Clc provided between a pixel electrode and a counter electrode; and a thin film transistor (TFT) whose gate electrode is connected to the gate signal line, source electrode is connected to the source signal line, and drain electrode is connected to the pixel electrode, wherein an auxiliary capacitor Cs is provided as necessary.
In a vicinity of the liquid crystal panel, source drivers are provided so as to correspond to the plurality of source signal lines respectively, and each of the source drivers supplies to corresponding source lines, a video signal corresponding to video display of each display pixel sections connected to the source signals. In order to prevent burning of liquid crystal, the video signal is such that positive polarity and negative polarity with respect to a counter electrode potential are alternately supplied. Such driving of the liquid crystal panel is referred to as “inversion driving”.
Further, in the vicinity of the liquid crystal panel, gate drivers are provided so as to correspond to the plurality of gate signal lines, wherein each of the gate drivers supplies to corresponding gate signal lines scanning signal for selectively driving a display pixel section connected to the gate signal line.
In each pixel section, when the scanning signal causes the TFT to be ON, the video signal is supplied to the pixel electrode via the TFT, and orientation of liquid crystal serving as a display medium sandwiched by both the electrodes varies according to a potential difference between a counter electrode potential and a pixel electrode potential, so that not only letters, symbols, and the like, but also various kinds of images are displayed in the display screen with entire pixel sections.
In the liquid crystal display device, each display pixel includes not only the liquid crystal capacitor Clc and the auxiliary capacitor Cs but also a source-drain parasitic capacitance Cgd of the TFT. Thus, in each pixel section, a charge pull-in voltage (charge pull-in amount) ΔV expressed by the following expression 1 occurs due to the gate-drain parasitic capacitance Cgd, so that a voltage actually applied to the liquid crystal varies so that the variation corresponds to the charge pull-in amount ΔV. Note that, in the following expression 1, VGH represents a gate high voltage of the scanning signal line, and VGL represents a gate low voltage of the scanning signal line.ΔV={Cgd/(Cgd+Clc+Cls)}×(VGH−VGL)
Further, the charge pull-in amount ΔV varies in the display screen of the liquid crystal panel, so that there occurs a flicker, that is, a displayed image flickers. Examples of the flicker include the following two types.    (1) In the liquid crystal panel, there are a wiring resistance and a parasitic capacitance in the gate signal line, so that a gate signal has a round waveform as further away from a signal input terminal side of the gate signal line. As a result, the charge pull-in amount ΔV varies due to the gate-drain parasitic capacitance Cgd of each pixel section. The variation of the charge pull-in amount ΔV causes occurrence of a deviation of a center value between a voltage applied to a liquid crystal layer at the time of positive driving in the display screen of the liquid crystal panel and a voltage applied to the liquid crystal layer at the time of negative driving, so that the flicker occurs.    (2) In the step of forming a pixel pattern on a glass substrate, it is difficult to form the pixel pattern on an entire surface of the glass substrate at once in case where the glass substrate has a large surface area, so that the surface area is divided into plural blocks and then formation of the pixel pattern is carried out plural times so as to correspond to the blocks. In this case, the gate-drain parasitic capacitance Cgd has a deviation in the display screen of the liquid crystal panel due to an alignment position or a pattern formation device's characteristic and the like. The deviation of the parasitic capacitance Cgd results in variation of the charge pull-in amount ΔV expressed by the aforementioned expression. Thus, there occurs a deviation of a center value between a voltage applied to a liquid crystal layer at the time of positive driving in the display screen of the liquid crystal panel and a voltage applied to the liquid crystal layer at the time of negative driving, so that the flicker occurs.
The flicker (1) is caused by the round waveform of the gate signal. Generally, the gate signal lines are disposed in a horizontal direction in the display screen, so that it is possible to reduce the flicker by correcting a slant of the charge pull-in amount ΔV in the horizontal direction.
Further, the flicker (2) is caused by a characteristic in the step of forming the pixel pattern. Thus, in case where formation of the pixel pattern is carried out plural times, it is possible to reduce the flicker by correcting the deviation of the charge pull-in amount ΔV in each formation block.
Further, Japanese Unexamined Patent Publication No. 22325/2001 (Tokukai 2001-22325) (Publication date: Jan. 26, 2001) (hereinafter, referred to as “Patent Document 1”) discloses a liquid crystal display device arranged so that an element which can obtain a desired resistance by an external input such as a potentiometer is provided on a gradation voltage generation circuit so as to be capable of adjusting a gradation characteristic without varying a circuit constant after designing a driving circuit.